With your own homemade sheet plastic vacuum former, you can (easily?) reproduce lots of different things for your wargames table, especially terrain features.
This video shows a neat build of a ruined tower terrain piece for your wargames table. It would work well for all sorts of genres and periods.
Barking Irons has a photo tutorial on making a stone barn for 28mm figures.
Maiwand Day has a nice photo essay on making a wargames mountain with a vertical profile. It’s really great looking, and is on my list of future projects
Massive Voodoo has an interesting tutorial on modeling realistic spider webs. It makes me think of Mirkwood.